The requirements for gummed tape, and especially reinforced gummed tape, are very severe. It must absorb water evenly and develop even tack, or else the tape will stick only in spots. It must, when remoistened, have a certain amount of "slip" to enable the user to adjust it slightly if it has not been placed in the correct position. Its initial tack must be fast, but the open time of the adhesive must be such that its tack is not lost if the operator is slow in using the moistened tape. It must not curl, and it must form a good bond with the surface to which it is applied.
Animal glue is an ideal adhesive for gummed tape. However, it is undesirable for many purposes because of its relatively high cost and the difficulty of obtaining supplies of consistent quality.
It is an object of this invention to provide a starch based adhesive that possesses tack properties similar to those of animal glue.
The combination of urea with certain oxidized waxy starch esters results in an adhesive suitable for gummed tape which will exhibit tack properties equivalent to those of animal glue.
The starch based adhesives used for gummed tape are prepared by heating the starch derivative with water and other additives (plasticizers, humectants, etc.) to a temperature between 85.degree. and 95.degree. C. for 15 to 30 minutes. The adhesive is then cooled to about 60.degree. to 70.degree. C. and applied to the tape by means of a roll coater or other application device. Thereafter, the tape is dried, rewound, and cut.